Semiconductor device

ABSTRACT

A semiconductor device includes an active fin on a substrate, a gate electrode and intersecting the active fin, gate spacer layers on both side walls of the gate electrode, and a source/drain region in a recess region of the active fin at at least one side of the gate electrode. The source/drain region may include a base layer in contact with the active fin, and having an inner end and an outer end opposing each other in the first direction on an inner sidewall of the recess region. The source/drain region may include a first layer on the base layer. The first layer may include germanium (Ge) having a concentration higher than a concentration of germanium (Ge) included in the base layer. The outer end of the base layer may contact the first layer, and may have a shape convex toward outside of the gate electrode on a plane.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. application Ser. No.16/272,265, filed Feb. 11, 2019, which claims benefit of priority toKorean Patent Application No. 10-2018-0085563 filed on Jul. 23, 2018 inthe Korean Intellectual Property Office, the disclosure of each of whichis incorporated herein by reference in its entirety.

BACKGROUND 1. Field

Inventive concepts relate to a semiconductor device.

2. Description of Related Art

As demand for high performance, high speed, and/or multifunctionality insemiconductor devices increases, a degree of integration ofsemiconductor devices has increased. When a semiconductor devicecorresponding to a high integration trend of a semiconductor device ismanufactured, the semiconductor device may include patterns having afine width or a fine separation distance. Moreover, in order to adjustfor operation characteristics due to a reduction in a size of a planarmetal oxide semiconductor FET (MOSFET), a semiconductor device includinga FinFET having a channel with a three-dimensional structure has beendeveloped.

SUMMARY

An aspect of inventive concepts is to provide a semiconductor devicehaving improved electrical characteristics.

According to an aspect of inventive concepts, a semiconductor deviceincludes: a substrate; an active fin on the substrate, the active finextending in a first direction, the active fin including a recessregion; a gate electrode on the substrate, the gate intersecting theactive fin such that the recess region of the active fin is at at leastone side of the gate electrode, the gate electrode extending in a seconddirection, the gate electrode including side walls; gate spacer layerson the side walls of the gate electrode; and a source/drain region therecess region of the active fin. The source/drain region may include abase layer in contact with the active fin and a first layer on the baselayer. The base layer may include an inner end and an outer end opposingeach other in the first direction. The base layer may be on an innersidewall of the recess region. The first layer may include germanium(Ge) having a concentration higher than a concentration of germanium(Ge) included in the base layer, and the outer end of the base layer maybe in contact with the first layer. The outer end of the base layer mayhave a shape convex toward outside of the gate electrode on a plane.

According to an aspect of inventive concepts, a semiconductor deviceincludes: a substrate; an active fin on the substrate, the active finextending in one direction on the substrate, the active fin including arecess region; a gate electrode on the substrate, the gate electrodeextending and intersecting the active fin such that the recess region ofthe active fin is at at least one side of the gate electrode; and asource/drain region in the recess region of the active fin. Thesource/drain region may include a first layer and a second layer havingdifferent concentrations of germanium (Ge). An end portion of the firstlayer, in which the first layer may be in contact with the second layeron an inner sidewall of the recess region, may have a region convextoward outside of the gate electrode on a plane.

According to an aspect of inventive concepts, a semiconductor deviceincludes: a substrate; an active fin on the substrate, the active finextending in one direction on the substrate, the active fin including arecess region; a gate electrode on the substrate, the gate electrodeextending and intersecting the active fin such that the recess region ofthe active fin is at at least one side of the gate electrode; and anepitaxial layer in the recess region of the active fin. At least one ofan end portion of the active fin or an end portion of the epitaxiallayer may have a region convex toward outside of the gate electrode on aplane. The end portion of the active fin may be defined by the recessregion in at least one side of the gate electrode.

BRIEF DESCRIPTION OF DRAWINGS

The above and other aspects, features and other effects of inventiveconcepts will be more clearly understood from the following detaileddescription, taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a plan view illustrating a semiconductor device according toexample embodiments;

FIGS. 2A to 2D are cross-sectional views illustrating a semiconductordevice according to example embodiments;

FIG. 3 is a partially enlarged plan view illustrating a semiconductordevice according to example embodiments;

FIGS. 4A and 4B are cross-sectional views illustrating a portion of asemiconductor device according to example embodiments;

FIGS. 5A to 6B are plan views and cross-sectional views illustrating asemiconductor device according to example embodiments;

FIGS. 7A and 7B are a plan view and a cross-sectional view illustratinga semiconductor device according to example embodiments;

FIG. 8 is a plan view illustrating a semiconductor device according toexample embodiments;

FIGS. 9A and 9B are a plan view and a cross-sectional view illustratinga semiconductor device according to example embodiments;

FIGS. 10A and 10B are a plan view and a cross-sectional viewillustrating a semiconductor device according to example embodiments;

FIGS. 11A to 20B are drawings illustrating a process sequence of amethod of manufacturing a semiconductor device according to exampleembodiments;

FIGS. 21A to 23B are drawings illustrating a process sequence of amethod of manufacturing a semiconductor device according to exampleembodiments;

FIG. 24 is a circuit diagram of a SRAM cell including a semiconductordevice according to example embodiments;

FIG. 25 is a block diagram illustrating an electronic device, includinga semiconductor device, according to example embodiments; and

FIG. 26 is a schematic diagram of a system including a semiconductordevice according to example embodiments.

DETAILED DESCRIPTION

Hereinafter, example embodiments of inventive concepts will be describedin detail with reference to the attached drawings.

FIG. 1 is a plan view illustrating a semiconductor device according toexample embodiments.

FIGS. 2A to 2D are cross-sectional views illustrating a semiconductordevice according to example embodiments. FIGS. 2A to 2D illustrate across-section of the semiconductor device of FIG. 1, taken along linesIIa-IIa′, IIb-IIb′, IIc-IIc′, and IId-II-d′. For convenience ofexplanation, only some components of a semiconductor device areillustrated in FIGS. 1 to 2D.

Referring to FIGS. 1 to 2D, a semiconductor device 100 may include asubstrate 101, active fins 105, element isolation layers 110,source/drain regions 150, a gate structure 160, and an interlayerinsulating layer 190. The gate structure 160 may include a gatedielectric layer 162, a gate electrode 165, and gate spacer layers 166.The semiconductor device 100 may include FinFET elements, a transistorin which the active fins 105 have a fin structure. The FinFET elementsmay include transistors disposed based on positions of the active fins105 and the gate structures 160, intersecting each other. For example,the transistors may be PMOS transistors.

The substrate 101 may have an upper surface extended in an X-directionand a Y-direction. The substrate 101 may include a semiconductormaterial, such as a Group IV semiconductor, a Group III-V compoundsemiconductor, or a Group II-VI compound semiconductor. For example, theGroup IV semiconductor may include silicon, germanium, orsilicon-germanium. The substrate 101 may be provided as a bulk wafer, anepitaxial layer, a Silicon-On-Insulator (SOI) layer, aSemiconductor-On-Insulator (SeOI) layer, or the like.

The element isolation layers 110 may define the active fins 105 in thesubstrate 101. The element isolation layers 110 may be formed using, forexample, a shallow trench isolation (STI) process. According to exampleembodiments, the element isolation layers 110 may include a regionextended deeper toward a lower portion of the substrate 101 between theactive fins 105. The element isolation layers 110 may have a curvedupper surface having a level becoming higher toward the active fins 105,but a shape of the upper surface of the element isolation layers 110 isnot limited thereto. The element isolation layers 110 may be formed ofan insulating material. The element isolation layers 110 may be, forexample, an oxide, a nitride, or a combination thereof.

The active fins 105 may be defined by the element isolation layers 110in the substrate 101, and may extend in a first direction, for example,the X-direction. The active fins 105 may have a structure of an activefin protruding from the substrate 101. An upper end of the active fins105 may protrude from an upper surface of the element isolation layers110 by a desired (and/or alternatively predetermined) amount. The activefins 105 may be formed of a portion of the substrate 101, and mayinclude an epitaxial layer grown from the substrate 101. Meanwhile, aportion of the active fins 105 on the substrate 101 may be recessed inboth sides of the gate structures 160, and source/drain regions 150 maybe disposed on the recessed active fins 105. Thus, as can be seen bycomparing FIGS. 2C and 2D, the active fins 105 may have a relativelyhigh height below the gate structure 160. According to exampleembodiments, the active fins 105 may include impurities.

The source/drain regions 150 may be disposed on recess regions RC, inwhich each of active fins 105 is recessed, in and/or adjacent to bothsides of the gate structures 160. The recess region RC is extended in anX-direction between the gate structures 160, and may have innersidewalls, located at both ends in an X-direction, and a bottom surfacebetween the inner sidewalls. The source/drain regions 150 may beprovided as a source region or a drain region of transistors. An uppersurface of the source/drain regions 150 may be located at a heightlevel, the same as or similar to a lower surface of the gate structures160, as illustrated in FIG. 2A. Meanwhile, a relative height of thesource/drain regions 150 and the gate structures 160 may be variouslychanged according to example embodiments. For example, the source/drainregions 150 may have a form of an elevated source/drain, in which anupper surface is located higher than a lower surface of the gatestructures 160, in detail, the gate electrodes 165.

The source/drain regions 150 may have a cross-section, taken in theY-direction, with a pentagon or a similar shape, as illustrated in FIG.2D. Meanwhile, in example embodiments, the source/drain regions 150 mayhave various shapes, for example, one among a polygon, a circle, and arectangle. Moreover, the source/drain regions 150 may have across-section, taken in the X-direction, of a flat upper surface, asillustrated in FIG. 2A, and may have a circular shape, an ellipticalshape, or a similar shape thereto, below the upper surface. Meanwhile,the shape described above may be variously changed in exampleembodiments according to a distance between adjacent gate structures160, a height of the active fins 105, or the like.

The source/drain regions 150 may include a base layer 151 and first tofifth layers 152, 153, 154, 155, and 156, sequentially stacked in therecess region RC. The base layer 151 and the first to fifth layers 152,153, 154, 155, and 156 may include silicon (Si), and may have differentconcentrations of germanium (Ge). Meanwhile, in example embodiments, thenumber of layers, forming the source/drain region 150, may be variouslychanged.

For example, the base layer 151 is only formed of silicon (Si), or mayfurther include germanium (Ge). When the base layer 151 includesgermanium (Ge), the concentration of germanium (Ge) may be lower thanthat of each of the first to fifth layers 152, 153, 154, 155, and 156,and may be higher than that of the active fin 105. For example, aconcentration of germanium (Ge) in the base layer 151 may be equal to orless than 20 at. %. In this specification, a concentration of germanium(Ge) refers to an atomic concentration (an atomic percentage). The baselayer 151 may further include doping elements such as boron (B) orgallium (Ga). In this case, the concentration of the doping elements maybe lower than that of each of the first to fifth layers 152, 153, 154,155, and 156, and may be higher than that of the active fin 105.

In the first to fourth layers 152, 153, 154, and 155, a concentration ofgermanium (Ge) may be increased upwardly. The first layer 152 includesgermanium (Ge) having a first concentration, the second layer 153includes germanium (Ge) having a second concentration, higher than thefirst concentration, the third layer 154 includes germanium (Ge) havinga third concentration, higher than the second concentration, and thefourth layer 155 may include germanium (Ge) having a fourthconcentration, higher than the third concentration. For example, thefirst concentration is in a range of 20 at. % to 40 at. %, the secondconcentration is in a range of 35 at. % to 55 at. %, the thirdconcentration is in a range of 45 at. % to 65 at. %, and the fourthconcentration is in a range of 50 at. % to 70 at. %. Moreover, in thefirst to fourth layers 152, 153, 154, and 155, a concentration of adoping element such as boron (B) or gallium (Ga) may be also increasedupwardly. The fifth layer 156 may include germanium (Ge) having aconcentration lower than that of the fourth layer 155, or may notinclude germanium (Ge). For example, the fifth layer 156 may be formedof silicon (Si), and may further include impurities other than silicon(Si), according to example embodiments.

The base layer 151 and the first to fifth layers 152, 153, 154, 155, and156 may have the same thickness or different thicknesses. For example,the base layer 151 and the fifth layer 156 may have a relatively thinthickness, while the third layer 154 may be formed to be relativelythick. The base layer 151 may have a thickness, for example, in a rangeof 3 nm to 5 nm.

At least one region of the base layer 151 is located below the gateelectrode 165, and at least one region of the first layer 152 may belocated below the gate spacer layer 166. On a plane, the base layer 151may have a region convex outwardly of the gate electrode 165. This willbe described in more detail below with reference to FIGS. 3 to 4B.

The gate structure 160 may be disposed above the active fins 105 to beextended in one direction, for example, the Y-direction, whileintersecting the active fins 105. A channel region of transistors may beprovided in the active fins 105, intersecting the gate structure 160.The gate structure 160 may include a gate dielectric layer 162, a gateelectrode 165, and gate spacer layers 166.

The gate dielectric layer 162 may be disposed between the active fins105 and the gate electrodes 165, and may be disposed to cover a lowersurface and both side surfaces of the gate electrodes 165.Alternatively, in some example embodiments, the gate dielectric layer162 may be only formed on a lower surface of the gate electrode 165. Thegate dielectric layer 162 may include an oxide, a nitride, or a high-kmaterial. The high-k material may refer to a dielectric material havinga dielectric constant, higher than a dielectric constant of a siliconoxide (SiO₂) film. The high-k material may be provided as one of analuminum oxide (Al₂O₃), a tantalum oxide (Ta₂O₃), a titanium oxide(TiO₂), a yttrium oxide (Y₂O₃), a zirconium oxide (ZrO₂), a zirconiumsilicon oxide (ZrSi_(x)O_(y)), a hafnium oxide (HfO₂), a hafnium siliconoxide (HfSi_(x)O_(y)), a lanthanum oxide (La₂O₃), a lanthanum aluminumoxide (LaAl_(x)O_(y)), a lanthanum hafnium oxide (LaHf_(x)O_(y)), ahafnium aluminum oxide (HfAl_(x)O_(y)), and a praseodymium oxide(Pr₂O₃).

The gate electrode 165 may include a conductive material, and mayinclude, for example, a metal nitride such as a titanium nitride film(TiN), a tantalum nitride film (TaN), or a tungsten nitride film (WN),and/or a metallic material such as aluminum (Al), tungsten (W),molybdenum (Mo), or the like, or a semiconductor material such as dopedpolysilicon. The gate electrodes 165 may include multilayer structuressuch as two or more layers. According to example embodiments, a cappinglayer may be further disposed above the gate electrode 165, and a lowersurface and side surfaces of the capping layer may be surrounded by thegate electrode 165 and the gate spacer layers 166, respectively.

The gate spacer layers 166 may be disposed on both side surfaces of thegate electrode 165. The gate spacer layers 166 may allow thesource/drain regions 150 to be isolated from the gate electrodes 165.The gate spacer layers 166 may have a multilayer structure according toexample embodiments. The gate spacer layers 166 may be formed of atleast one of an oxide, a nitride, or an oxynitride, in detail, a low-kfilm.

The interlayer insulating layer 190 may be disposed to cover uppersurfaces of the element isolation layers 110, the source/drain regions150, and the gate structures 160. The interlayer insulating layer 190may include, for example, at least one among an oxide, a nitride, and anoxynitride, and may include a low-k material. A material of theinterlayer insulating layer 190 may be different than a material of thegate spacer layer 160.

FIG. 3 is a partially enlarged plan view illustrating a semiconductordevice according to example embodiments. In FIG. 3, a ‘C’ region of FIG.1 is enlarged and illustrated.

FIGS. 4A and 4B are cross-sectional views illustrating a portion of asemiconductor device according to example embodiments. FIGS. 4A and 4Billustrate a cross-section of the semiconductor device of FIG. 3, takenalong lines A-A′ and B-B′, respectively.

First, referring to FIG. 3, an active fin 105, a source/drain region 150disposed in a recess region RC of the active fin 105, and a gatestructure 160 are illustrated. In detail, in FIG. 3, the arrangement ona plane, of the base layer 151 and the first to fifth layers 152, 153,154, 155, and 156, forming the source/drain region 150, is illustratedin detail.

The recess region RC of the active fin 105 is formed to be extendeddownwardly of the gate structures 160 between the gate structure 160,and an end portion thereof in the X-direction may be located below thegate structure 160. The end portion of the recess region RC may have ashape concave outwardly of the gate structure 160. In other words, theend portion of the recess region RC may have a shape of which a width isincreased from a lower portion of the gate structure 160 toward a sidesurface or a side wall of the gate structure 160.

The base layer 151 is disposed at a lowermost portion of the recessregion RC, and may be disposed to be in contact with inner sidewalls anda bottom surface of the recess region RC. Thus, an inner end 151E1 ofthe base layer 151 may have a shape concave outwardly in a mannersimilar to the end portion of the recess region RC. In thisspecification, in the description of the source/drain regions 150, an‘end portion’ is used as an expression referring to a point on an innersidewall of the recess region RC, in contact with other vertical layers.Moreover, in the description of the end portion, a portion closer to thecenter based on the center of the gate structure 160 or the gateelectrode 165 in the X-direction is referred to as an ‘inner side,’ anda portion remote from the center is referred to as an ‘outer side.’ Anouter end 151E2 of the base layer 151 may have a shape convex outwardlyof the gate structure 160 or the gate electrode 165. According toexample embodiments, a portion of the outer end 151E2 of the base layer151 may coincide with a crystal plane of the active fin 105. However,even in this case, surfaces, growing in the X-direction from the baselayer 151, may not be formed of facets formed along a crystal plane, andfacets may at least have a relaxed form. For example, when an uppersurface of the substrate 101 or the active fin 105 is a <100> direction,the base layer 151 may not only be formed of facets such as a {111}facet in a <110> direction, corresponding to the X-direction.

The first layer 152 may be disposed on the base layer 151, and the innerend 152E1 of the first layer 152 may be substantially the same as theouter end 151E2 of the base layer 151. Thus, the inner end 152E1 of thefirst layer 152 may have a shape convex outwardly of the gate structure160 or the gate electrode 165. The outer end 152E2 of the first layer152 may also have a shape convex outwardly of the gate structure 160 orthe gate electrode 165, and a surface in the X-direction may not beformed of facets. The first layer 152 is formed on the base layer 151,not having facets, and may thus not have facets. Thus, the uniformity ofa thickness in the recess region RC may be improved. At least a portionof the base layer 151 and the first layer 152 may be disposed below thegate spacer layer 166 on a plane.

The second layer 153 may be disposed on the first layer 152, and mayhave an outer end with a shape convex toward an outer region of the gateelectrodes 165. However, a position of the outer end is not limitedthereto. A width of the second layer 153 in the Y-direction may besimilar to or greater than that of the first layer 152. The third tofifth layers 154, 155, and 156 may be sequentially disposed on thesecond layer 153, and the relative positional relationship of the secondto fifth layers 153, 154, 155, and 156 may be variously changed inexample embodiments.

Referring to FIGS. 4A and 4B, in an inner end 151E1 of the base layer151, an outermost portion EC illustrated in FIG. 4A, closest to thecenter of the gate electrode 165 in the X-direction, may be locatedbelow the gate electrode 165. Moreover, at least a portion of the firstlayer 152 may be located below the gate spacer layer 166. On an innersidewall of the recess region RC, the inner end 151E1 of the base layer151 and the inner end 152E1 of the first layer 152 may have a regionextended perpendicularly to an upper surface of the substrate 101.Alternatively, on the inner sidewall of the recess region RC, an innerside surface of the base layer 151 and an inner side surface of thefirst layer 152 may have a region extended perpendicularly to the uppersurface of the substrate 101.

A length L1 of the active fin 105 in the center of the active fin 105 inthe Y-direction, illustrated in FIG. 4A, may be shorter than a length L2of an active fin in an edge, illustrated in FIG. 4B. A separationdistance D1 between a side surface of the gate electrode 165 and anoutermost portion EC of the base layer 151 in the center of the activefin 105 in the Y-direction between the source/drain regions 150 may begreater than a separation distance D2 in an edge. Moreover, a length L3between outer ends 151E2 of both base layers 151 of the gate electrode165, in the center of the active fin 105 in the Y-direction, illustratedin FIGS. 3 and 4A, may be greater than a length L4 between outer ends151E2 in an edge, illustrated in FIGS. 3 and 4B.

At least a portion the second to fifth layers 153, 154, 155, and 156 maybe located below the gate spacer layer 166, but is not limited thereto.Each of the base layer 151 as well as the first layer 152 and the secondlayer 153 may have a uniform thickness in the recess region RC, or mayhave a different thickness according to a region. The third layer 154may have a relatively thick thickness as compared with other layers. Thefourth 155 and the fifth layer 156 may be disposed in a region adjacentto an upper surface of the source/drain region 150, and may have arelatively thin thickness as compared with other layers.

The first layer 152 does not have a facet. Thus, upper layers includingthe second layer 153 formed above the first layer 152 may have improveduniformity of a thickness, as compared with the case in which it isformed above facets. When the first layer 152 has facets, the secondlayer 153 may be formed relatively thicker on a bottom surface of therecess region RC. However, according to example embodiments, in thesecond layer 153, a thickness on a side wall of the active fin 105 maynot be significantly different from a thickness on a bottom surface ofthe recess region RC, and may be substantially uniform.

The first to third layers 152, 153, and 154 may serve to apply stress toa channel region of a transistor. Thus, according to exampleembodiments, layers including the first layer 152 and the second layer153 are formed to have a uniform thickness, and an inner side surface ofthe base layer 151 and an inner side surface of the first layer 152 havea region perpendicular to an upper surface of the substrate 101. Thus,stress is uniformly transferred to a channel region, so electricalcharacteristics of a semiconductor device such as resistance of achannel region, drain induced barrier lowering (DIBL) characteristics,and the like, may be improved. Moreover, as compared to the case inwhich it is formed above facets, for example, a volume of the thirdlayer 154 may be relatively increased. When the third layer 154functions as a main layer for applying stress to a channel region, ifthe volume of the third layer 154 is increased, stress may besufficiently applied to the channel region.

FIGS. 5A to 6B are plan views and cross-sectional views illustrating asemiconductor device according to example embodiments. In FIGS. 5A to6B, regions corresponding to those of the FIGS. 3 and 4A areillustrated.

Referring to FIGS. 5A and 5B, in a source/drain region 150 a of asemiconductor device 100 a, an outermost portion EC of a base layer 151may be located below an interface between the gate electrode 165 and thegate dielectric layer 162 or outside thereof. For example, the outermostportion EC of the base layer 151 may be located below the gatedielectric layer 162. At least a portion of the first layer 152 may belocated below the gate spacer layer 166. At least a portion the secondto fifth layers 153, 154, 155, and 156 may be located below the gatespacer layer 166, but is not limited thereto. In example embodiments,the third to fifth layers 154, 155, and 156 may not be located below thegate spacer layer 166.

Referring to FIGS. 6A and 6B, in a source/drain region 150 b of asemiconductor device 100 b, a first layer 152 may include a regionlocated outside of a lower portion of a gate spacer layer 166 on a sidewall of an active fin 105. In other words, an outer end 152E2 of thefirst layer 152 may be located externally as compared with the gatespacer layer 166 on a plane. Thus, the second to fifth layers 153, 154,155, and 156 may not be located below the gate spacer layer 166 on aside wall of the active fin 105.

In a manner similar to that described with reference to FIGS. 5A to 6B,in example embodiments, a position of the inner end 151E1 of the baselayer 151, a position of an inner end 152E1 and an outer end 152E2 of afirst layer 152, and the like may be variously changed.

FIGS. 7A and 7B are a plan view and a cross-sectional view illustratinga semiconductor device according to example embodiments. In FIGS. 7A to7B, regions corresponding to those of the FIGS. 3 and 4A areillustrated.

Referring to FIGS. 7A and 7B, a source/drain region 150 c of asemiconductor device 100 c, in a manner different from the exampleembodiment of FIGS. 1 to 4B, may not include a base layer 151. Thesource/drain region 150 c may be formed of first to fifth layers 152,153, 154 155, and 156. Moreover, an end portion of a recess region RCaof the active fin 105 may have a shape convex outwardly of the gatestructure 160 on a plane. In other words, the end portion of the recessregion RCa may have a shape of which a width is decreased toward a sidewall of the gate structure 160. As described above, when the end portionof the recess region RCa has a shape convex outwardly of the gatestructure 160, even though the source/drain region 150 c does notinclude the base layer 151, electrical characteristics of thesemiconductor device 100 c may be secured.

The first layer 152 may be disposed in the recess region RCa to be incontact with the active fin 105. At least a portion of the first layer152 may be located below the gate spacer layer 166. However, a positionof the first layer 152 is not limited thereto. For example, in exampleembodiments, the first layer 152 may be located below the gate electrode165. An inner end 152E1 and an outer end 152E2 of the first layer 152may have a shape convex outwardly of the gate structure 160 or the gateelectrode 165. End portions of the second layer 153 may have a shapeconvex outwardly.

FIG. 8 is a plan view illustrating a semiconductor device according toexample embodiments. In FIG. 8, a region corresponding to that of FIG. 3is illustrated.

Referring to FIG. 8, a source/drain region 150 d of a semiconductordevice 100 d, in a manner different from the example embodiment of FIGS.1 to 4B, may not include a base layer 151. The source/drain region 150 dmay be formed of first to fifth layers 152, 153, 154 155, and 156.Moreover, an end portion of a recess region RCb of an active fin 105 mayhave a shape substantially parallel to a side wall of a gate structure160 on a plane. As described above, when the end portion of the recessregion RCa has a shape extended to be flat in the Y-direction of thegate structure 160, even though the source/drain region 150 d does notinclude the base layer 151, electrical characteristics of thesemiconductor device 100 d may be secured.

The first layer 152 may be disposed in the recess region RCb to be incontact with the active fin 105. At least a portion of the first layer152 may be located below the gate spacer layer 166. However, a positionof the first layer 152 is not limited thereto. For example, in exampleembodiments, the first layer 152 may be located below the gate electrode165. The inner end 152E1 of the first layer 152 may have a linear shapesubstantially parallel to a side wall of the gate structure 160. Anouter end 152E2 of the first layer 152 may have a shape convex outwardlyof the gate structure 160 or the gate electrode 165. However, accordingto example embodiments, the outer end 152E2 of the first layer 152 mayhave a linear shape substantially parallel to a side wall of the gatestructure 160.

FIGS. 9A and 9B are a plan view and a cross-sectional view illustratinga semiconductor device according to example embodiments. FIG. 9Billustrates a cross-section of the semiconductor device of FIG. 9A,taken along lines IId1-IId1′ and IId2-IId2′.

Referring to FIGS. 9A and 9B, a semiconductor device 100 e may include asubstrate 101 having a first region I and a second region II, a firstactive fin 105A and a second active fin 105B, element isolation layers110, first source/drain regions 150A and second source/drain regions150B, a gate structure 160, and an interlayer insulating layer 190. Inthe semiconductor device 100 e, PMOS transistors may be disposed in thefirst region I, while NMOS transistors may be disposed in the secondregion II.

The active fins 105A and the second active fins 105B may be disposed inthe first region I and the second region II, respectively, and mayinclude impurities having different conductivity types. According toexample embodiments, the gate structures 160 may have differentstructures in the first region I and the second region II. For example,materials and work functions of the gate electrodes 165 may bedifferent.

The first source/drain regions 150A and the second source/drain regions150B may be disposed in the first region I and the second region II,respectively. The first source/drain regions 150A and the secondsource/drain regions 150B may be formed of semiconductor materialshaving different conductivity types. For example, the first source/drainregions 150A may include silicon germanium (SiGe) doped with a p-typeimpurities, while the second source/drain regions 150B may includesilicon (Si) doped with an n-type impurities. The second source/drainregions 150B may not include germanium (Ge). The description of thesource/drain region 150, described with reference to FIGS. 2 to 4D, maybe similarly applied to the first source/drain regions 150A. The secondsource/drain regions 150B may be formed of a single layer, or mayinclude a plurality of regions including doping elements with differentconcentrations.

As illustrated in FIG. 9B, the first source/drain regions 150A and thesecond source/drain regions 150B may have shapes with differentcross-sections. For example, the first source/drain regions 150A mayhave a pentagon or a shape similar thereto, while the secondsource/drain regions 150B may have a hexagon or a shape similar thereto.

FIGS. 10A and 10B are a plan view and a cross-sectional viewillustrating a semiconductor device according to example embodiments.FIG. 10B illustrates a cross-section of the semiconductor device of FIG.10A, taken along line IId-IId′.

Referring to FIGS. 10A and 10B, in a semiconductor device 100 f,source/drain regions 150 may be connected or merged to each other on twoactive fins 105 to form a single source/drain region 150. However, thenumber of active fins 105, disposed below a single source/drain region150 connected as described above is not limited to that illustrated inthe drawing, and may be variously changed in example embodiments.

For example, in the source/drain region 150 f, a base layer 151 as wellas a first layer 152 and a second layer 153 may be disposed on eachactive fin 105, and third to fifth layers 154, 155, and 156 may have aconnected form on two active fins 105. Thus, the planar arrangement ofthe base layer 151 as well as the first layer 152 and the second layer153 may be the same as that according to an example embodiment of FIGS.1 to 4D.

FIGS. 11A to 20B are drawings illustrating a process sequence of amethod of manufacturing a semiconductor device according to exampleembodiments. In FIGS. 11A to 20B, a method for manufacturing thesemiconductor device described above with reference with FIGS. 1 to 2Dwill be described.

Referring to FIGS. 11A and 11B, a substrate 101 is patterned to formactive fins 105 and element isolation layers 110.

First, a mask layer for patterning the substrate 101 is formed on thesubstrate 101, and the substrate 101 is anisotropically etched using themask layer to form trenches TI. The trenches TI may be formed in aregion except for the active fins 105. The trenches TI have a highaspect ratio, and thus may have a width becoming narrower downwardly.Thus, the active fins 105 may have a shape becoming narrower upwardly.

Then, an operation of filling the trenches TI with an insulatingmaterial and planarizing may be performed. Then, the insulatingmaterial, with which the trenches TI is filled, is partially removed, sothe active fins 105 may protrude from the element isolation layer 110.The operation described above may be performed using, for example, a wetetching process. Thus, the active fins 105 may protrude from an upperportion of the element isolation layer 110 by a desired (and/oralternatively predetermined) height, and a protruding height may bevariously changed in example embodiments.

Referring to FIGS. 12A and 12B, sacrificial gate structures 170 may beformed in the active fins 105 and the element isolation layer 110.

The sacrificial gate structures 170 may be a sacrificial layer formed ina region in which the gate dielectric layer 162 and the gate electrode165 are disposed as illustrated in FIG. 1 through a subsequentoperation. The sacrificial gate structures 170 may be patterned to havea shape of a line extended in the Y-direction while intersecting theactive fins 105.

The sacrificial gate structure 170 may include a first sacrificial layer172 and a second sacrificial layer 174 as well as a mask pattern layer176, sequentially stacked. The mask pattern layer 176 may be a hard masklayer remaining after the first sacrificial layer 172 and the secondsacrificial layer 174 are patterned. The first sacrificial layer 172 andthe mask pattern layer 176 may be an insulating layer, while the secondsacrificial layer 174 may be a conductive layer, but an exampleembodiment is not limited thereto. For example, the first sacrificiallayer 172 may include a silicon oxide, the second sacrificial layer 174may include polysilicon, and the mask pattern layer 176 may include asilicon nitride. The number of layers forming the sacrificial gatestructure 170 and the material thereof may be variously changedaccording to example embodiments.

Referring to FIGS. 13A and 13B, gate spacer layers 166 may be formed onside surfaces of the sacrificial gate structures 170.

A spacer forming material is deposited to a uniform thickness along anupper surface and/or a side surface of the active fins 105, the elementisolation layers 110, and the sacrificial gate structures 170, and thenmay be anisotropically etched to form the gate spacer layers 166.

The gate spacer layers 166 may be formed of an insulating material. Forexample, the gate spacer layers 166 may be formed of a low dielectricconstant material, and may include at least one among SiO, SiN, SiCN,SiOC, SiON, and SiOCN. In example embodiments, the gate spacer layers166 may have a structure in which a plurality of films are stacked.During formation of the gate spacer layers 166, a spacer may be alsoformed on a side surface of the active fins 105.

Referring to FIGS. 14A and 14B, the active fins 105 are recessed betweenthe sacrificial gate structures 170 to form recess regions RC.

The active fins 105, having been exposed, are recessed to a desired(and/or alternatively predetermined) depth from an upper surface of theactive fins between the sacrificial gate structures 170, to form therecess regions RC. The recess process may be performed by sequentiallyapplying a dry etching process and a wet etching process, for example.Thus, the active fins 105 may have a lower level between the sacrificialgate structures 170, as compared a level of the active fins below thesacrificial gate structures 170.

The recess regions RC may be extended toward lower portions of the gatespacer layers 166 and the sacrificial gate structures 170. Thus, therecess regions RC may be formed over an expanded region, as comparedwith a space between the gate spacer layers 166, in the active fins 105.In the recess regions RC, end portions in the X-direction may be locatedbelow the gate spacer layers 166 and the sacrificial gate structures 170on a plane, and may have a shape concave outwardly of the sacrificialgate structures 170. According to example embodiments, both ends of anupper surface of the recess regions RC are located below the gate spacerlayers 166 or the sacrificial gate structures 170, and thus may includean undercut region.

Selectively, after the recess regions RC are provided, an operation ofcuring a recessed surface of the active fins 105 may be performed usinga separate operation. Moreover, before or after the recess operation, anoperation of injecting impurities into the active fins 105 may beperformed. The impurity injection operation may be performed using thesacrificial gate structures 170 and the gate spacer layers 166 as amask.

Referring to FIGS. 15A and 15B, the base layers 151 of the source/drainregions 150 may be provided in the recess regions RC.

The base layers 151 may be grown from the active fins 105, using aselective epitaxial growth (SEG) process, for example. The base layers151 may be, for example, a silicon (Si) layer. Alternatively, the baselayers 151 may be, for example, a silicon germanium (SiGe) layer. Inthis case, the base layers may include germanium (Ge) having aconcentration lower than that of the first layer 152 to be formedthereabove. The base layers 151 may further include doping elements suchas boron (B), and a concentration of the doping elements may be higherthan that in the active fins 105. The doping elements may be in-situdoped during the growth of the base layers 151, or may be separatelyinjected after the growth.

The base layers 151 may be formed on the entirety of the surface of therecess regions RC, and an outermost portion EC may be located below thesacrificial gate structures 170. According to etching conditions, adistance between the sacrificial gate structures 170, a width of theactive fins 105, and the like, a shape, on a plane, of the inner end151E1 in which the base layers 151 are in contact with active fins 105on an inner sidewall of the recess regions RC may be variously changed.However, in this case, the inner end 151E1 may have a shape generallyconcave outwardly of the sacrificial gate structures 170. The baselayers 151 may have the outer end 151E2, illustrated by a dotted line inFIG. 15A, on an inner sidewall of the recess regions RC, and the outerend 151E2 may have a convex curved shape without facets.

Referring to FIGS. 16A and 16B, first layers 152 may be formed on thebase layers 151 of the source/drain regions 150.

The first layers 152 may be formed using, for example, a SEG process.The first layers 152 may be, for example, a silicon germanium (SiGe)layer. For example, when the base layers 151 are the silicon germanium(SiGe) layer, the first layers 152 may include germanium (Ge) having aconcentration higher than that of the base layers 151. The first layers152 may further include doping elements such as boron (B).

The first layers 152 may be formed on a surface of the base layers 151in the recess regions RC, and an outermost portion, in contact with thebase layers 151 on a plane may be located below the gate spacer layers166. The inner end 152E1 of the first layers 152 may have a shapegenerally convex outwardly of the sacrificial gate structures 170. Thefirst layers 152 are formed on the base layers 151, not having facets,so even an outer end 152E2, not in contact with the base layers 151, mayalso have a convex shape without facets.

Referring to FIGS. 17A and 17B, second to fifth layers 153, 154, 155,and 156 are formed on the first layers 152, so source/drain regions 150may be provided.

The second to fifth layers 153, 154, 155, and 156 may be formed using,for example, a SEG process. The second to fourth layers 153, 154, and155 may be, for example, a silicon germanium (SiGe) layer, while thefifth layers 156 may be a silicon (Si) layer. In the second to fourthlayers 153, 154, and 155, a concentration of germanium (Ge) may beincreased sequentially. The second to fifth layers 153, 154, 155, and156 may further include doping elements such as boron (B). In the secondto fourth layers 153, 154, and 155, a concentration of doping elementsmay be increased sequentially.

The second layers 153 may be formed on a surface of the first layers152, and the third layers 154 may be formed relatively thick so as tomostly fill the recess regions RC. The fourth and fifth layers 155 and156 may be formed relatively thin on a surface of the recess regions RC.

The source/drain regions 150 may have a greater width in the Y-directionon a plane between the sacrificial gate structures 170 than a widthbelow the sacrificial gate structures 170, and may have a region ofwhich a width is increased.

Referring to FIGS. 18A and 18B, an interlayer insulating layer 190 isformed above sacrificial gate structures 170, gate spacer layers 166,element isolation layers 110, and source/drain regions 150, and firstand second sacrificial layers 172 and 174 may be removed therefrom.

After an insulating material is deposited to cover the sacrificial gatestructures 170, the gate spacer layers 166, the element isolation layers110, and the source/drain regions 150, an upper surface of the secondsacrificial layers 174 is exposed through a planarizing process, so theinterlayer insulating layer 190 may be provided. Thus, a mask patternlayer 176 of the sacrificial gate structures 170 may be removed at thisoperation. The interlayer insulating layer 190 may include, for example,at least one among an oxide, a nitride, and an oxynitride, and mayinclude a low-k material.

Then, the first and second sacrificial layers 172 and 174 of thesacrificial gate structures 170 are selectively removed with respect tothe element isolation layer 110 and the active fins 105, locatedtherebelow, so an opening GR, exposing the element isolation layer 110and the active fins 105, may be provided. A removal operation of thefirst and second sacrificial layers 172 and 174 may be at least one of adry etching process and a wet etching process.

Referring to FIGS. 19A and 19B, gate dielectric layers 162 and gateelectrodes 165 are formed in the opening GR, thereby ultimately forminggate structures 160.

The gate dielectric layers 162 may be formed substantially conformallyalong a side wall and a lower surface of the opening GR. The gatedielectric layers 162 may include an oxide, a nitride, or a high-kmaterial. The gate electrodes 165 may be formed to fill a space insidethe gate dielectric layers 162. The gate electrodes 165 may include ametal or a semiconductor material.

After the gate dielectric layers 162 and the gate electrodes 165 areformed, a material remaining on the interlayer insulating layer 190 maybe removed therefrom using a planarizing process such as a chemicalmechanical polishing (CMP) process.

Referring to FIGS. 20A and 20B, the interlayer insulating layer 190 ispatterned to form contact holes, and a conductive material may beembedded in the contact holes to form contact plugs 180.

First, an upper insulating layer 195 may be further formed on theinterlayer insulating layer 190 and the gate structures 160. Then, aseparate mask layer such as a photoresist pattern may be formed, and theinterlayer insulating layer 190 and the upper insulating layer 195 areremoved from both sides of the gate structure 160, so the contact holesmay be provided. A lower surface of the contact holes may allow at leasta portion of the source/drain regions 150 to be recessed.

Then, a conductive material is deposited in the contact holes, socontact plugs 180, electrically connected to the source/drain regions150, may be provided. Before deposition of the conductive material,impurities may be injected into a lower portion of the contact holes toreduce contact resistance. Thus, a concentration of impurities in aregion adjacent to a lower end of the contact plugs 180 may be increasedas compared with a concentration of impurities after formation of thesource/drain regions 150. In example embodiments, a shape and placementof the contact plugs 180 may be variously changed.

FIGS. 21A to 23B are drawings illustrating a process sequence of amethod of manufacturing a semiconductor device according to exampleembodiments. In FIGS. 21A to 23B, a method for manufacturing thesemiconductor device described above with reference with FIGS. 7A to 7Bwill be described.

Referring to FIGS. 21A and 21B, the active fins 105 are recessed betweenthe sacrificial gate structures 170 to form recess regions RCa.

First, the operations described above with reference to FIGS. 11A to 13Bare performed in the same manner, so active fins 105, sacrificial gatestructures 170, and gate spacer layers 166 may be provided.

Then, the active fins 105, having been exposed, are recessed to adesired (and/or alternatively predetermined) depth from an upper surfaceof the active fins between the sacrificial gate structures 170, to formthe recess regions RCa. The recess process may be performed using a dryetching process and/or a wet etching process, for example. The recessregions RCa may be extended toward lower portions of the gate spacerlayers 166 and the sacrificial gate structures 170 in the active fins105. In the recess regions RCa, end portions in the X-direction may belocated below the gate spacer layers 166 on a plane, and may have ashape convex outwardly of the sacrificial gate structures 170. However,in the recess regions RCa, a position of the end portions in theX-direction on a plane may be changed according to example embodiments,and may be located below the sacrificial gate structures 170.

Referring to FIGS. 22A and 22B, the first layers 152 of the source/drainregions 150 may be provided in the recess regions RCa.

The first layers 152 may be grown from the active fins 105, using theSEG process, for example. The first layers 152 may be, for example, asilicon germanium (SiGe) layer. The first layers 152 may further includedoping elements such as boron (B).

The first layers 152 may be formed on the entirety of the surface of therecess regions RCa, and an outermost portion EC may be located below thegate spacer layers 166. The inner end 152E1 of the first layers 152, incontact with the active fins 105, may have a shape generally convexoutwardly of the sacrificial gate structures 170 on a plane according toa shape of the recess regions RCa. The first layers 152 may have theouter end 152E2, illustrated by an alternate long and short dash line inFIG. 22A, on an inner sidewall of the recess regions RCa, and the outerend 152E2 may have a convex curved shape without facets.

Referring to FIGS. 23A and 23B, second to fifth layers 153, 154, 155,and 156 are formed on the first layers 152, so source/drain regions 150c may be provided.

The second to fifth layers 153, 154, 155, and 156 may be provided usinga process similar to that described above with reference to FIGS. 17Aand 17B. Thus, the source/drain regions 150 c, including the first tofifth layers 152, 153, 154, 155, and 156, may be provided.

FIG. 24 is a circuit diagram of a SRAM cell including a semiconductordevice according to example embodiments.

Referring to FIG. 24, in the SRAM element, a single cell may be formedof first and second driving transistors TN1 and TN2, first and secondload transistors TP1 and TP2, as well as first and second accesstransistors TN3 and TN4. In this case, a source of the first and seconddriving transistors TN1 and TN2 may be connected to a ground voltageline Vss, while a source of the first and second load transistors TP1and TP2 may be connected to a power supply voltage line Vdd.

The first driving transistor TN1, formed of an NMOS transistor, and thesecond load transistor TP1, formed of a PMOS transistor, may form afirst inverter, while the second driving transistor TN2, formed of anNMOS transistor, and the second load transistor TP2, formed of a PMOStransistor, may form a second inverter. At least a portion of the firstand second load transistors TP1 and TP2 may include a semiconductordevice according to various example embodiments, as described above withreference to FIGS. 1 to 10B.

An output terminal of the first and second inverters may be connected toa source of the first access transistor TN3 and the second accesstransistor TN4. Moreover, the first and second inverters may beconnected to each other to form a single latch circuit while an inputterminal and an output terminal are crossed. In addition, drains of thefirst and second access transistors TN3 and TN4 may be connected tofirst and second bit lines BL and/BL.

FIG. 25 is a block diagram illustrating an electronic device, includinga semiconductor device, according to example embodiments.

Referring to FIG. 25, an electronic device 1000 according to an exampleembodiment may include a communications unit 1010, an input unit 1020,an output unit 1030, a memory 1040, and a processor 1050.

The communications unit 1010 may include a wired/wireless communicationsmodule such as a wireless Internet module, a local communicationsmodule, a global positioning system (GPS) module, or a mobilecommunications module. The wired/wireless communications module includedin the communications unit 1010 may be connected to an externalcommunications network based on various communications standards totransmit and receive data.

The input unit 1020 may include a mechanical switch, a touchscreen, avoice recognition module, and the like, as a module provided for a userto control operations of the electronic device 1000. In addition, theinput unit 1020 may also include a mouse or a finger mouse deviceoperating based on a trackball or a laser pointer, and may furtherinclude various sensor modules which enable a user to input data.

The output unit 1030 may output information processed by the electronicdevice 1000 in an audio or video format, and the memory 1040 may store aprogram for processing or control of the processor 1050, or data. Theoutput unit 1030 may include at least one of a speaker, an antenna, aconnection structure (e.g., terminal, microUSB, etc.) and the like foroutputting information to an electronic device. The processor 1050 maysend an instruction to the memory 1040 depending on a required operationto store or retrieve data to/from the memory 1040.

The memory 1040 may be embedded in the electronic device 1000, or maycommunicate with the processor 1050 through an additional interface.When the memory 1040 communicates with the processor 1050 through theadditional interface, the processor 1050 may store data in or retrievedata from the memory 1040 through various interface standards such assecure digital (SD), secure digital high capacity (SDHC), secure digitalextended capacity (SDXC), micro SD, universal serial bus (USB), etc.

The processor 1050 controls operation of each component included in theelectronic device 1000. The processor 1050 may perform control andprocessing associated with a voice call, a video call, datacommunications, and the like, or may conduct control and processing formultimedia reproduction and management. The processor 1050 may alsoprocess an input entered by a user through the input unit 1020 andoutput a result thereof through the output unit 1030. Furthermore, theprocessor 1050 may store or retrieve data required to control operationsof the electronic device 1000 to/from the memory 1040 as describedabove. At least one of the processor 1050 and the memory 1040 mayinclude a semiconductor device according to various example embodiments,as described above with reference to FIGS. 1 to 10B.

FIG. 26 is a schematic diagram of a system including a semiconductordevice according to example embodiments.

Referring to FIG. 26, a system 2000 may include a controller 2100, aninput/output (I/O) device 2200, a memory 2300, and an interface 2400.The system 2000 may be a mobile system, or a system transmitting orreceiving information. The mobile system may be a personal digitalassistant (PDA), a portable computer, a tablet PC, a wireless phone, amobile phone, a digital music player, a memory card, and the like.

The controller 2100 may function to execute a program and control thesystem 2000. The controller 2100 may be, for example, a microprocessor,a digital signal processor, a microcontroller, or devices similarthereto.

The I/O device 2200 may be used to input or output data of the system2000. The system 2000 may use the I/O device 2200 to be connected to anexternal device, such as, a personal computer or a network,communicating data with the external device. The I/O device 2200 may be,for example, a keypad, a keyboard, or a display.

The memory 2300 may store a code and/or data for operations of thecontroller 2100, and/or may store data processed by the controller 2100.

The interface 2400 may be a data transfer path between the system 2000and other external devices. The controller 2100, the I/O device 2200,the memory 2300, and the interface 2400 may communicate with each otherusing a bus 2500.

At least one of the controller 2100 or the memory 2300 may include asemiconductor device according to various example embodiments, asdescribed above with reference to FIGS. 1 to 10B.

As set forth above, according to example embodiments of inventiveconcepts, a structure and a shape of a source/drain region arecontrolled, so a semiconductor device having improved electricalcharacteristics may be provided.

While example embodiments have been shown and described above, it willbe apparent to those skilled in the art that modifications andvariations could be made without departing from the scope of the presentdisclosure, as defined by the appended claims.

What is claimed is:
 1. A semiconductor device, comprising: a substrate;an active fin on the substrate, the active fin extending in a firstdirection, the active fin including a recess region; a gate electrode onthe substrate, the gate electrode intersecting the active fin such thatthe recess region of the active fin is adjacent to at least one side ofthe gate electrode, the gate electrode extending in a second direction;and a source/drain region in the recess region of the active fin, thesource/drain region including a base layer in contact with the activefin and a first layer on the base layer, the base layer including aninner end and an outer end opposing each other in the first direction,the base layer on an inner sidewall of the recess region, the base layerand the first layer having different concentrations of germanium (Ge),the outer end of the base layer being in contact with the first layer,and the outer end of the base layer having a shape convex outwardlytoward outside of the gate electrode on a plane parallel to an uppersurface of the substrate, wherein the base layer includes boron (B) orgallium (Ga) having a concentration higher than a concentration of boron(B) or gallium (Ga) in the active fin, wherein the outer end of the baselayer is in the recess region of the active fin.
 2. The semiconductordevice of claim 1, wherein the base layer has a thickness in a range ofabout 3 nm to about 5 nm.
 3. The semiconductor device of claim 1,wherein the source/drain region has a first width in the seconddirection and a second width in the second direction, the first width isin a region adjacent to the gate electrode, the second width is in aregion spaced apart from the gate electrode, and the second width isgreater than the first width.
 4. The semiconductor device of claim 1,wherein the first layer includes germanium (Ge) having a concentrationhigher than a concentration of germanium (Ge) in the base layer.
 5. Thesemiconductor device of claim 1, wherein at least a portion of the innerend of the base layer is below the gate electrode.
 6. The semiconductordevice of claim 1, wherein the first layer has an inner end and an outerend opposing each other in the first direction on the inner sidewall ofthe recess region, and the outer end of the first layer has a regionconvex outwardly of the gate electrode on a plane.
 7. The semiconductordevice of claim 1, wherein the base layer is formed of silicon (Si). 8.The semiconductor device of claim 1, wherein the outer end of the baselayer is not defined by a crystal plane of the active fin.
 9. Thesemiconductor device of claim 1, wherein the first layer is a silicongermanium (SiGe) layer including germanium (Ge) in a range of 20 at. %to 40 at. %.
 10. The semiconductor device of claim 1, wherein thesource/drain region further includes a second layer on the first layer,the second layer fills the recess region, and the second layer includesgermanium (Ge) having a concentration higher than a concentration ofgermanium (Ge) in the first layer.
 11. The semiconductor device of claim1, wherein the inner end of the base layer includes a region extendingperpendicularly to an upper surface of the substrate.
 12. Thesemiconductor device of claim 1, wherein the base layer includesgermanium (Ge) having a concentration higher than a concentration ofgermanium (Ge) in the active fin.
 13. A semiconductor device,comprising: a substrate; an active fin on the substrate, the active finextending in a first direction on the substrate; a gate electrode on thesubstrate, the gate electrode extending in a second direction andintersecting the active fin; and a source/drain region on the activefin, the source/drain region including a first layer and a second layerhaving different concentrations of germanium (Ge), an end portion of thefirst layer, in which the first layer is in contact with the secondlayer, having a region convex toward outside of the gate electrode on aplane parallel to an upper surface of the substrate, wherein the endportion of the first layer is in a recess region of the active fin,wherein the source/drain region has a first width in the seconddirection and a second width in the second direction, the first width isin a region adjacent to the gate electrode, the second width is in aregion spaced apart from the gate electrode, and the second width isgreater than the first width.
 14. The semiconductor device of claim 13,further comprising: a base layer below the first layer, wherein the baselayer contacts the active fin, and the base layer includes germanium(Ge) having a concentration lower than a concentration of germanium (Ge)included in the first layer.
 15. The semiconductor device of claim 14,wherein an end portion of the base layer, in which the base layer is incontact with the active fin, has a region concave toward outside of thegate electrode on a plane.
 16. The semiconductor device of claim 13,further comprising: a contact plug on the source/drain region, whereinthe contact plug is connected to the source/drain region.
 17. Thesemiconductor device of claim 13, wherein the substrate includes aSilicon-On-Insulator (SOI) layer.
 18. A semiconductor device,comprising: a substrate including a Silicon-On-Insulator (SOI) layer; anactive fin on the substrate, the active fin extending in one directionon the substrate; a gate electrode on the substrate, the gate electrodeextending and intersecting the active fin; and an epitaxial layer on theactive fin at least one side of the gate electrode, wherein an endportion of the epitaxial layer is in a recess region of the active fin,and at least one of, an end portion of the active fin, in contact withthe epitaxial layer, or the end portion of the epitaxial layer, has aregion convex toward outside of the gate electrode on a plane parallelto an upper surface of the substrate.
 19. The semiconductor device ofclaim 18, further comprising: a first layer and a second layer on theepitaxial layer, wherein the first layer and the second layer havedifferent concentrations of germanium (Ge), and the epitaxial layer, thefirst layer, and the second layer form a source/drain region.
 20. Thesemiconductor device of claim 19, wherein the epitaxial layer includesgermanium (Ge) having a concentration lower than a concentration ofgermanium (Ge) in the first layer.